The master-slave model is a type of communication where one device or process (e.g., a master device) has unidirectional control over one or more other devices (e.g., a slave device). In some systems, a master is elected from a group of eligible devices, with the other devices acting in the role of slaves. There are multiple possible applications of the master-slave communication model. Described below are some examples of such applications:                Railway locomotives operating in multiple (e.g., to pull loads too heavy for a single locomotive) can be referred to as a master-slave configuration with the operation of all locomotives in the train slaved to the controls of the first locomotive.        In database replication, the master database is regarded as the authoritative source, and the slave databases are synchronized to it.        Peripherals connected to a bus in a computer system.        Duplication is often done with several cassette tape or compact disc recorders linked together. Operating the controls on the master triggers the same commands on the slaves, so that recording is done in parallel.        In parallel ATA hard drive arrangements, the terms master and slave are used but neither drive has control over the other. The terms also do not indicate precedence of one drive over the other in most situations. “Master” is merely another term for device 0 and “slave” indicates device 1.        
As indicated, one application of the master-slave model is in public transportation and/or traffic management. Today, public transportation consists of a variety of modes including buses, trolleys, subways, trains, and ferries. Along with the various modes of transportation, there exists a variety of payment methods for the transportation fare. Accepted payment methods for public transportation may include tickets, tokens, cash, credit cards, debit cards, etc. Automated systems have attempted to make the payment process simpler and more efficient. Automated fare collection (AFC) system is the name given to automated transportation ticketing systems. Typically, AFC systems are connected to the information systems in vehicles, at stations or other transportation centers. Unfortunately, challenges may exist in providing optimal communication between master device and slave devices in a public transportation environment.
U.S. Pat. No. 7,957,402 discloses bridging communications between user datagram protocol and transmission control protocol.
U.S. Pat. No. 7,694,051 discloses detecting master-slave response time-out under continuous packet format communications protocol.
U.S. Pat. No. 7,529,241 discloses a network bridge for user datagram protocol multicast traffic.
U.S. Pat. No. 7,460,482 discloses a master-slave communications system for a communication switch.
U.S. Pat. No. 7,356,018 discloses a communication system including a master station communication device along with multiple slave station communication devices.
U.S. Patent Application 20090113232 discloses an apparatus for managing a plurality of wireless sensor networks.
U.S. Patent Application 20060251046 discloses a master-slave synchronization communication system.